Megger 230425 User manual

AVTM23-4J

Rev 2

Dec 2010

Instruction Manual

AC/DC

High Pot Testers

Catalog No. 230425 & 230425-1

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AC/DC

High Pot Testers

Catalog No. 230425 & 230425-1

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Copyright© 2010 by Megger. All rights reserved.

The information presented in this manual is believed to be adequate for the
intended use of the product. If the product or its individual instruments are
used for purposes other than those specified herein, confirmation of their
validity and suitability must be obtained from Megger. Refer to the warranty
information below. Specifications are subject to change without notice.

WARRANTY

Products supplied by Megger are warranted against defects in material and
workmanship for a period of one year following shipment. Our liability is
specifically limited to replacing or repairing, at our option, defective
equipment. Equipment returned to the factory for repair must be shipped
prepaid and insured. Contact your MEGGER representative for instructions
and a return authorization (RA) number. Please indicate all pertinent
information, including problem symptoms. Also specify the serial number and
the catalog number of the unit. This warranty does not include batteries, lamps
or other expendable items, where the original manufacturer’s warranty shall
apply. We make no other warranty. The warranty is void in the event of abuse
(failure to follow recommended operating procedures) or failure by the
customer to perform specific maintenance as indicated in this manual.

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Table of Contents

1.0 INTRODUCTION ................................................................................. 1

2.0 SAFETY PRECAUTIONS ................................................................... 3

Equipment Safety Precautions ................................................................. 3

General Safety Precautions for DC Testing ........................................... 7

3.0 RECEIVING INSTRUCTIONS ......................................................... 9

4.0 SPECIFICATIONS .............................................................................. 11

Physical Characteristics ............................................................................ 11

Environmental Recommendations ........................................................ 11

Input ........................................................................................................... 12

Input Protection ....................................................................................... 12

Output ........................................................................................................ 13

AC Mode: .............................................................................................. 13

DC Mode: ............................................................................................. 13

Metering ..................................................................................................... 14

Controls ..................................................................................................... 14

Voltage Control ................................................................................... 14

Mode Selection ..................................................................................... 15

Failure Detection and Automatic Shutdown .................................. 16

Indicators ................................................................................................... 17

Accessories ................................................................................................ 17

Test Connections ...................................................................................... 17

Tests Performed ....................................................................................... 18

Tester Grounded ................................................................................. 18

Dielectric Voltage-Withstand ............................................................ 18

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5.0 DESCRIPTION .....................................................................................19

Control and Connector Identification ...................................................19

6.0 OPERATION ........................................................................................25

Test Area ....................................................................................................25

Suggestions .................................................................................................26

Preliminary Routine ..................................................................................27

Shutdown Procedure ................................................................................27

Operating Notes ........................................................................................28

Operating Procedure ................................................................................29

7.0 APPLICATION NOTES .....................................................................35

Properties of Insulation ...........................................................................35

Leakage Current ................................................................................... 35

Insulation Failure ......................................................................................37

Dielectric Voltage-Withstand Test Characteristics ..............................38

Output .................................................................................................... 38

Instructions for Setting the Leakage Sensitivity Control ....................42

AC Testing ............................................................................................ 42

DC Testing .................................................................................................43

Dielectric Withstand Testing of Low VAC Appliances .....................45

8.0 MAINTENANCE .................................................................................47

Routine Maintenance ................................................................................47

Mechanical Inspection (Exterior) ...................................................... 47

Mechanical Inspection (Interior) ............................................................48

Electrical Inspection .................................................................................49

Calibration ..................................................................................................57

Setup ....................................................................................................... 57

Calibration Procedure ..............................................................................58

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9.0 TROUBLESHOOTING GUIDE ..................................................... 61

Repairs ........................................................................................................ 61

10.0 REPLACEABLE PARTS LIST ......................................................... 67

11.0 WARRANTY & REPAIR .................................................................. 75

Warranty ..................................................................................................... 75

Repairs ........................................................................................................ 75

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List of Figures

Figure 1 Megger AC/DC High Pot Tester .................................. v

Figure 2 Controls and Connectors ............................................. 24

Figure 3 Typical Output Characteristics of the Megger

AC/DC High Pot Tester in the AC Mode. ........................... 40

Figure 4 Typical Output Characteristics of the Megger

AC/DC High Pot Tester in the DC Mode. ........................... 41

Figure 5 Internal View of Tester ................................................ 63

Figure 6 Schematic Diagram of Megger ACV/DC High Pot

Testers 230425 & 230425-1 ..................................................... 75

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

Figure 1 Megger AC/DC High Pot Tester, Catalog No. 230425

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DANGER!

The high voltages produced by this equipment can be
extremely dangerous!

Any equipment to be tested must first be disconnected
from its power supply.

All personnel must be kept clear of connections and
bare parts of equipment where high voltages may be
present.

SAFETY IS THE RESPONSIBILITY OF THE
USER.

All users of this equipment should read and
understand this manual before operating the
equipment and should follow all safety instructions.

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1.0

INTRODUCTION

This instruction manual covers the operation and
maintenance of the Megger portable AC/DC High Pot
Tester. The input and output characteristics of the tester
are indicated by its catalog number, as follows:

230425 120V, 50/60 Hz input, 4 kV AC output or

230425-1 240V, 50/60 Hz input, 4 kV AC output or 5

This compact, self-contained unit is a high-voltage, low­energy source for testing the dielectric strength of electrical
insulation. Dielectric withstand (high-pot) testing of
electrical insulation is a valuable method of detecting
assembly flaws (such as stray wire strands, etc.) and defects
in marginally sound insulation. Such conditions can be
hazardous to the user and may cause product failure
during normal use.

5 kV DC output

kV DC output

The Tester has been designed to simplify testing
procedures and to minimize hazards to both the operator

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and the item under test. The Tester meets all standards for
sensitivity, voltage regulation and failure detection

currently required by Underwriters Laboratories
test equipment used in production line voltage-withstand
testing of electrical appliances and components.

The instructions and suggestions provided in this manual
anticipate the normal use of the Tester for testing electrical
insulation systems on motors, transformers and most line­operated electrical appliances.

(UL) for

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2.0

SAFETY PRECAUTIONS

SAFETY IS THE RESPONSIBILITY OF THE USER

La seguridad es la responsabilidad del operador

Equipment Safety Precautions

WARNING

F

The voltages and currents produced by the tester
can cause harmful or fatal electric shock to the
user or bystander. For your protection, follow all
Safety Procedures given in this manual.

The Megger AC/DC High Pot Tester has been designed
with careful attention to safety. Megger has conducted
formal safety reviews of the initial equipment design and
all subsequent changes. This procedure, followed for all
new instruments, covers areas in addition to those
included in the American National Standards Institute
(ANSI) standard.

®

Because hazards exist with all electrical test equipment,
proper procedures and precautions must be observed by
the user when operating this instrument. The basic safety

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procedures to be followed when operating this equipment
are given in this section. Additional safety instructions are
provided in other sections as appropriate. In addition, the
instrument has been marked with precautionary warnings.

Safety notations used in this manual and on the instrument
indicate various degrees of hazard to personnel or
equipment. The notations are listed below, with brief
explanations of how they are applied.

G
F
g

CAUTION

Cautions alert you to possible damage to
equipment.

WARNING
Warnings alert you to conditions that are
potentially hazardous to people.

EARTH GROUND

Marking on Instrument

V

NOTE: Notes provide important information.

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DANGEROUS VOLTAGE

Marking on Instrument

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Safety Precautions

Before using the Tester, read and understand this entire
instruction manual. When operating the Tester, carefully
follow the testing procedures given in this manual and all
applicable safety instructions, with special emphasis on
those that follow:

1. Provide a dry test area, with operator and all

equipment shielded from traffic and onlookers.

2. Perform tests on a secure insulated mounting area.

The insulation must

isolate the item to be tested

from ground and from any adjacent conductors.

3. Place the item under test out of the operator’s

normal reach. Treat the item under test as a shock
hazard until it is proven safe by tests performed in
accordance with procedures given in this manual.

4. Plug in the high-voltage test probe assembly (Wl)

only when it is being used. Handle its clips only by
the insulators; never touch the clips directly

! At the
completion of a test, do not touch the clips until
the voltage shown on the voltmeter is zero (0).
Unplug the high-voltage test probe assembly from
the Tester during periods when testing is not
actively being done and before leaving the test
area.

5. For all tests, connect the black lead of the high-

voltage test probe assembly (Wl) first. Connect

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and disconnect the item under test only when high
voltage is off.

6. Practice test procedures until they become familiar

before actually performing tests on equipment.

7. Unskilled personnel who use the Tester should be

trained in a fixed operating routine for each test
setup and supervised by a person who fully
understands the operation of the Tester.

8. Do not use the Tester or any of its accessories for

any purposes other than those described in this
manual.

9. Never operate the Tester with its case removed;

dangerous voltages are present within the
instrument.

10. Have only qualified personnel to repair the Tester.

Observe all precautions and follow the procedures
in Section 9.0 Troubleshooting Guide.

11. Maintain the Tester with a regular maintenance

program.

The Tester may be used in a great variety of applications,
thus it is not possible to foresee every potential hazard that
may arise. To insure safe use of all equipment involved in a
test, always treat it carefully. It is essential that the user
addition to following all safety instructions in this manual,

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, in

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Safety Precautions

carefully consider all safety aspects of each test before it is
performed.

For further details on safety practices and precautions for
high-voltage and high-power testing, refer to IEEE
Standard 510-1983; IEEE Recommended Practices for Safety in
High-Voltage and High-Power Testing.

General Safety Precautions for DC Testing

In addition to the basic safety practices described above,
observe the following precautions when conducting DC
tests.

1. When not in use, devices insulated by solid or

solid/liquid dielectric should be grounded and
short-circuited with bonding jumpers.

2. Capacitive objects should be short-circuited as

follows:

a) If any capacitive object not in use might be within

the influence of a DC electric field, its exposed
high-voltage terminal should be grounded.
Otherwise, the DC electric field may induce a
voltage in the capacitive object.

b) Capacitive objects with a solid dielectric should be

short-circuited after DC proof testing. Otherwise,
dielectric absorption in the insulation may result in

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NOTE

a buildup of voltage on the object. The short
circuit should remain on the object until the

dielectric absorption has dissipated or until the object

has been reconnected to a circuit.

: All capacitive devices should remain short-

circuited when not in use.

c) Any open-circuited capacitive device should be

short-circuited and grounded before it is touched
by personnel.

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3.0

RECEIVING INSTRUCTIONS

READ COMPLETELY BEFORE OPERATING

When your Megger instrument arrives, check the
equipment received against the packing list. Notify
Megger, Norristown, PA 19403 of any shortage of
materials.

Examine the instrument for damage received in transit. If
any damage is found, file a claim with the carrier at once
and notify Megger or its nearest authorized sales
representative. Be sure to provide a detailed description of
the damages observed.

Your Megger instrument has been thoroughly tested and
inspected to rigid specifications before being shipped and
is ready for use when set up as indicated in Section 6.0,
Operation.

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4.0

SPECIFICATIONS

Physical Characteristics

Dimensions: 8-3/8” D x 9” W x 8-1/8” H

(213 x 229 x 206 mm)

Weight: 13.5 lbs. (6.1 kg)

Environmental Recommendations

Operating
Temperature:

Storage
Temperature:

Humidity: Operation and storage limits 5

Climate: Operation prohibited in direct rain or

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25°F to 104°F (-4°C to 40°C)

-22°F to 131°F (-30°C to 55°C)

to 95% RH

snow

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Input

230425: 120 volts ±10%, 1A, 50/60 Hz single

230425-1: 240 volts ±10%, 0.5A, 50/60 Hz single

Input Protection

phase with ground.

Connection to the Tester is made via a
removable 7-1/2 ft. power cord; with a
molded PVC grounding plug PH-290B
(NEMA configuration 5-l5P) on one end
and a molded PVC grounding connector
SPH-386 on the other.

phase with ground.

Connection to the Tester is made via a
removable 6-1/2 ft. power cord; with a
molded PVC grounding plug PH-44
(NEMA configuration 6-15P) on one end
and a molded PVC grounding connector
SPH-386 on the other.

2-pole, 1 Amp, 250V, rocker handle circuit breaker

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Output

AC Mode:

Specifications

0-4000 VAC:
Maximum short-

circuit current:
Maximum load

at maximum
voltage:

Maximum capacitive loads are proportionally higher at
reduced output voltages. (See Figure 3 in Section 7.0,
Application Notes)

DC Mode:

0-5000 VDC:

Maximum
current:

Maximum
ripple:

NOTE
load.

For complete loading capability, see Figure 4 in Section 7.0,
Application Notes.

continuously adjustable

12.6 mA (electronic limitation)

0.008 µF (60 Hz), 0.010 µF (50 Hz)

continuously adjustable, negative
polarity with respect to ground

12.6 mA (electronic limitation)

0.4% RMS per mA at full voltage (no
capacitive load)

: Ripple will be greatly reduced with a capacitive

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Metering

Average reading, RMS calibrated

Style: 3-1/2’, zero left analog meter with high-

Range: 0-5000 V

Accuracy: ±2% Full Scale

Controls

Voltage Control

Voltage is controlled manually by means of an adjustable
autotransformer with zero-start interlock.

torque, ruggedized movement

(NOTE: AC readings stop at 4 kV.)

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Mode Selection

Four pushbuttons provide the following selections.

Specifications

One Second Test

: Momentary actuation of the ONE

SEC pushbutton turns on high voltage for a period of
from 1 second (minimum) to 1.3 seconds (maximum)
unless a failure occurs. This test is recommended for AC
testing only, since DC testing usually involves a high initial
charging current which may cause a failure signal. To begin
initial testing, or after a failure, the RESET pushbutton
must be actuated or the VOLTAGE CONTROL returned
to the ZERO START (RESET) position. Once the Tester
is reset, the One-Second Test can be repeated as many
times as desired.

Continuous Test

: Momentary actuation of the CONT

pushbutton turns on high voltage until the HV OFF
pushbutton is actuated or a failure occurs. Each time high
voltage is turned off, or after a failure, the RESET
pushbutton must be actuated or the VOLTAGE
CONTROL returned to the ZERO START (RESET)
position.

HV Off

: Momentary actuation of the HV OFF

pushbutton turns off high voltage.

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Reset: Momentary actuation of the RESET
pushbutton stops failure signals and allows further testing.

NOTE: The RESET pushbutton is also a zero-

start override. When the output voltage has
been preset and the HV OFF pushbutton
has been depressed, high voltage can be
turned on to the preset value by depressing
the RESET button then the CONT or
ONE SEC test pushbutton.

Failure Detection and Automatic Shutdown

The failure detection circuit indicates a failure, by audible
and visual alarms, and switches off high voltage within 50
ms whenever arcing occurs or the total leakage current
exceeds a preset value. The leakage current trip level for
AC output, is adjustable between 0.32 mA ±5% to 12.3
mA ±5% by means of the LEAKAGE SENSITIVITY
control knob. For DC output, is adjustable between 0.41
mA ±5% to 10.1 mA ±5% by means of the LEAKAGE
SENSITIVITY control knob.

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Indicators

Specifications

Tester
Grounded:

HV On: Lights when the high-voltage output is

Power: Integral to power switch. Lights when

Failure: Lights when a breakdown occurs or an

Audible Alarm: Sounds when the failure lamp is lit.

Accessories

Catalog No.
230425-2

Test Connections

The item to be tested is connected by means of the
alligator clips on the 4-ft. long removable high-voltage test
probe assembly.

Lights when the Tester is connected to a
properly wired supply

energized

power is available to the Tester.

excessive leakage current is drawn by
the item under test.

Removable high-voltage test probe
assembly, 4 feet long, with retractile test
tips.

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Tests Performed

Tester Grounded

A low current (less than 0.5 mA, 120 V operation) line
monitoring circuit is connected between the “HOT” side
and the ground side of the incoming power line. This
circuit lights a white neon lamp as soon as the Tester is
connected to a correctly wired power supply. The
grounded circuit of the Tester is interlocked with the
dielectric voltage- withstand test so that high voltage
cannot be applied if either of the following common faults
exist:

a) Ground wire open.

b) “HOT and “NEUTRAL” wires interchanged

(120V operation).

Dielectric Voltage-Withstand

A high-voltage transformer supplies test voltage to two
panel jack assemblies. A slide selects the desired panel jack
assembly (either AC or DC) and automatically connects
the proper metering circuit. A high-voltage test probe
assembly plugs into the open panel jack assembly for
output. A voltmeter indicates the test voltage. Visual and
audible alarms signal when the total leakage current
exceeds an adjustable preset value or when arcing occurs.

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5.0

DESCRIPTION

Control and Connector Identification

The locations of controls and connectors and their
schematic reference numbers are shown in Figure 2. Their
functions are described below.

CB1 - Input Circuit Breaker/Power Switch

This circuit breaker controls the power input to the Tester.
It disconnects the power circuit if more than 1 ampere is
drawn by the Tester.

DS1 - Power

This indicator is an integral part of the Input Circuit
Breaker/Power Switch (CBl). It lights when power is
available to the Tester.

DS2 - Failure

This indicator lights and an audible alarm sounds when a
breakdown occurs or an excessive leakage current is drawn
by the item under test.

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DS3 - HV On

This indicator lights when high voltage is available to the
Output Receptacle (J8) and the high-voltage test probe
receptacle (J9).

DS5 - Tester Grounded

This indicator lights when the Tester is connected to a
correctly wired power supply.

: Since the current through this lamp is

NOTE

limited to 0.5 mA (120V operation), this
lamp will not be as bright as the other
indicators.

J8 - AC Output Receptacle

This receptacle accepts the high-voltage test probe
assembly (W1) for AC high-voltage testing.

J9 - DC Output Receptacle

This receptacle accepts the high-voltage test probe
assembly (W1) for DC high-voltage testing.

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Descriptions

M1 - Kilovoltmeter

This meter shows the voltage being applied to the item
under test.

P7 – Input Inlet

This inlet accepts the input power cord (W3).

R77 – Leakage Sensitivity

This variable potentiometer allows the leakage current trip
level to be set between 0.3 mA and 12 mA.

S1 – One Sec

This pushbutton initiates the one-second high-voltage test.

NOTE

: This test is recommended for AC testing

only, since DC testing usually involves a
high initial charging current which may
cause a failure signal.

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S2 - Cont

This pushbutton is provided for high-voltage testing for
any desired length of time. When this button is used, high
voltage remains on until the HV OFF pushbutton is
depressed or a failure occurs.

S3 – HV Off

This pushbutton switches off high voltage. It may be used
at any time.

S4 - Reset

This pushbutton stops failure signals and allows further
testing.

T3 – Voltage Control

This autotransformer serves as voltage control, reset, and
zero start.

W1 - High-Voltage Test Probe Assembly (not shown)

This lead assembly plugs into either the AC or DC output
receptacle (J8 or J9) for high-voltage testing.

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Descriptions

W2 - Input Power Cord (not shown)

This cord plugs into the input inlet (P7). It is provided
with an outboard end appropriate to the input voltage
requirement (l20V or 240V).

Output Receptacle Slide

This slide connects voltmeter (Ml) to either the AC or the
DC circuit.

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Figure 2 Controls and Connectors

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6.0

OPERATION

Follow all safety precautions given in Section 2.0 of this
manual.

Test Area

Wherever the Tester is used, the test area should be
arranged according to the following guidelines.

SAFETY PRECAUTIONS

1. Select a dry test area where the operator and all

equipment are shielded by suitable barriers from
traffic and onlookers.

2. Locate the Tester within six feet of a 3-wire

grounded outlet and within four feet of the item
to be tested.

3. Provide a secure insulated mounting area for the

item to be tested. The insulation must isolate the
item to be tested from ground and from any
adjacent conductors. If the insulation of the
mounting area is questionable, a rubber electrical­grade insulation mat or a suitable piece of acrylic
plastic or phenolic can be used as insulation.

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NOTE: Rubber gloves or shoes are not required, but

Suggestions

A sturdy wood workbench is recommended for the test
area. A simple support may be used to hold the entire
Tester in a convenient position, with the Tester case
secured to the support. A space on the workbench may be
arranged so that the item to be tested can be clamped
securely in place and insulated from ground.

4. Place the item to be tested out of the operator’s

normal reach. Arrange the work area so that the
operator can reach the controls of the Tester
without any danger of touching the item under
test.

Megger considers their use an excellent safety
practice when handling the item under test.

Barriers are strongly recommended to prevent accidental
contact with the item under test.

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Preliminary Routine

Before conducting any test, carry out the following
routine:

1. Review any damage report that has been

submitted covering the item to be tested.

2. Visually inspect the item to be tested.

Operation

3. Repair any visible defects before

Shutdown Procedure

To remove high voltage from the item under test, set the
power switch (CB1) to the OFF position or depress and
release the HV OFF pushbutton.

At the completion of a test, when voltage has
been switched off, do NOT touch the high-voltage

F

test probe assembly alligator clips until the
voltage shown on the voltmeter is 0.

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testing.

WARNING

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Operating Notes

High voltage cannot be switched on unless the following
interlock conditions are met:

1. The TESTER GROUNDED lamp (DS5) must be

lit.

2. The VOLTAGE CONTROL (T3) must be in the

ZERO START (RESET) position or the RESET
pushbutton (S4) must be depressed.

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Operating Procedure

To insure safety and accurate test results, observe the
following procedure when operating the Tester;

1. With the power switch (CB1) off, connect the input

power cord (W2) to the Tester INPUT inlet (P7); then
plug the input power cord (W2) into a grounded
outlet.

2. Verify that the TESTER GROUNDED lamp (DS5) is

lit.

If the tester grounded lamp (DS5) is not lit, do
not proceed any further. Unplug the input

G

3. To connect the item under test, attach the high-

power cord (W2) and refer to Section 9.0,
Troubleshooting Guide.

voltage test probe assembly (W1) to either the AC or
DC OUTPUT receptacle (J8 or J9). Connect the black
lead of the high-voltage test probe assembly (W1) to
the low (or ground or return) side of the item under
test. Connect the red lead to the high potential side of
the item under test.

Operation

CAUTION

4. Set the LEAKAGE SENSITIVITY control (R77) to

the desired setting. Refer to SECTION 7.0,

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5. Turn the, power switch (CB1) on. The switch should

6. To enable high-voltage testing, set the VOLTAGE

7. Select the desired test, either one-second or

NOTE

APPLICATION NOTES for detailed instructions for
setting this control.

light.

CONTROL (T3) to the ZERO START (RESET)
position or press the RESET pushbutton (S4).

continuous.

: The one-second test is recommended for AC

testing only, since the high initial charging
current usually present in DC testing may
cause a failure signal.

a) CONTINUOUS TEST

1. Press the CONT pushbutton (S2). The HV ON

lamp (DS3) will light.

F

2. While observing the kilovoltmeter (M1) indication,

raise the voltage to the desired level by rotating

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WARNING
The tester is now capable of producing high­voltage.

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Operation

the VOLTAGE CONTROL (T3) clockwise.
Maintain the selected voltage level for the required
time.

NOTE: In a DC test, increasing voltage too fast may

cause a failure signal.

3. To end the test, return the VOLTAGE

CONTROL (T3) to the ZERO START (RESET)
position; then press the HV OFF pushbutton (S3).
The HV ON lamp (DS3) will go out.

WARNING

Do not proceed until the kilovoltmeter (M1)

F

This test is used when several identical items are being
tested.

reads 0.

b) One-Second Test

1. With the item under test connected, set the

voltage as for the continuous test (A2 above), but
press the HV OFF pushbutton (S3) without
returning the VOLTAGE CONTROL (T3) to the
ZERO START (RESET) position.

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F

8. To proceed with additional testing after the HV OFF

9. During high-voltage testing, be alert to failure

2. To start a series of one-second tests, press the

RESET pushbutton (S4); then press the ONE
SEC pushbutton (S1) each time a test is to be
performed.

3. To end a series of tests, return the VOLTAGE

CONTROL (T3) to the ZERO START (RESET)
position and press the HV OFF pushbutton (S3).

WARNING
Do not proceed until the kilovoltmeter (M1)

reads 0.

pushbutton (S3) has been pressed, return the
VOLTAGE CONTROL (T3) to the ZERO START
(RESET) position or press the RESET pushbutton
(S4).

symptoms such as the sounding of the audible alarm,
lighting of the FAILURE lamp (DS2), a sudden
voltage drop, or an erratic kilovoltmeter (M1) reading.

10. When the Tester detects a failure, the audible

sounds, the

voltage is switched off.

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alarm

FAILURE lamp (DS2) lights and high

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To turn off the failure signals and continue testing,
return the VOLTAGE CONTROL (T3) to the
ZERO START (RESET) position or press the
RESET pushbutton (S4).

Operation

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7.0

APPLICATION NOTES

Properties of Insulation

Leakage Current

All electrical insulating structures, when subjected to
voltage, conduct some current. When alternating voltage is
applied, this current is made up of two components: one
due to conduction through or across the surface of the
insulator (the resistive), and one due to the capacitance of
the structure (the capacitive). Both of these components
are undesirable and by design are kept very small in new
equipment. Nevertheless, some current of both types
always “leaks” around or through any insulator, hence the
name “leakage current.” (Under some definitions, only the
resistive component is called leakage, but this manual
follows current practice by also including the capacitive).

Leakage current of both resistive and capacitive
components increases with voltage and generally with the
size of equipment. Capacitive current, in particular, is high
for items that have windings (motors, transformers) or
long runs of wire (wired control panels, etc.). In good new

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equipment, the resistive component is usually much
smaller than the capacitive.

Leakage that occurs during a dielectric voltage-withstand
test (high-voltage leakage) should not be confused with the
leakage that occurs when an appliance is energized at its
normal operating voltage and for which limits are specified
by various safety standards, such as UL. This operating
leakage is an important safety consideration, but it is
related only indirectly to high-voltage leakage and is
normally much smaller. Operating leakage cannot be
measured by a high pot tester. Other Megger instruments
are available for measuring this line-voltage leakage
current. The term ‘leakage current” is used in this manual
to refer to high-voltage leakage current.

The schematic diagram below represents the leakage
current paths during a dielectric voltage-withstand test. In
good equipment, I

is usually much less than IC.

R

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Insulation Failure

When defective insulation is subjected to a high voltage,
one of two things happens:

a) Leakage current increases greatly because part of

the insulation has become conductive.

b) A spark jumps across an air gap which has

become too short to withstand the applied
voltage,

Condition (a) may lead to (b), and (b) usually leads to a
continuing “breakdown” discharge which emits light, heat,
and a crackling sound and carries as much current as the
Tester will deliver, causing the detection circuit to signal a
failure. Such a discharge also causes high-frequency (RF)
variations in the current which are useful in detection.

Failure is often caused by defects such as:

Application Notes

a) Dirt on the insulation, which causes increased

resistive current. This may heat the surface and
cause a further increase and may lead to a
discharge.

b) Cracks or pinholes in insulation, which usually

lead to a quick breakdown and discharge.

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c) Shortened air gap due to defective assembly,

which may cause discharge across the gap. An
example is a loose strand of wire near the frame.

d) Insulation saturated with moisture. This condition

may cause a large increase in either component of
leakage current.

Dielectric Voltage-Withstand Test Characteristics

Output

Figure 3, a graph showing output voltage and capacitance,
illustrates the typical output characteristics of the Tester in
the AC mode. Figure 4, a graph showing output voltage
and output current, illustrates the typical output
characteristics of the Tester in the DC mode.

Automatic Failure Detection

The Tester is equipped with a failure detection circuit that
detects insulation failure in the form of excessive leakage
current or an arcing fault. The leakage current trip level is
adjustable between 0.3 mA and 12 mA by the LEAKAGE
SENSITIVITY control (R77). The Tester indicates a
failure by the audible alarm and the FAILURE lamp
(DS2), and it switches off high voltage within 50 ms.

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Application Notes

Occasionally the operator may detect a visible or audible
discharge or erratic voltmeter indication without an
accompanying failure signal from the Tester. These
represent borderline cases in which the discharge energy
remains small and does not build up to a full breakdown.
If such indications are observed repeatedly during a test
period, they should be considered signs of failure.

If a single “snap” or “pop” occurs and is not repeated, it
may be due to a stray projection or dirt which has burned

off, in which case the item under test may be acceptable.

Such weak “pops” seldom occur at higher test voltages or
with high-capacitance test items. However, some complex
structures, such as relays and transformers, may emit a
more continuous buzz at high voltage. This is a very low
energy “corona” discharge and generally not a sign of
insulation

failure.

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Figure 3 Typical Output Characteristics of the Megger AC/DC

High Pot Tester in the AC Mode.

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Application Notes

.05

Figure 4 Typical Output Characteristics of the Megger AC/DC

High Pot Tester in the DC Mode.

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Instructions for Setting the Leakage Sensitivity
Control

AC Testing

Set the LEAKAGE SENSITIVITY control (R77)
according to the capacitance of the item under test, if
known. Follow the guidelines given below:

Capacitance of Item Unknown

If the capacitance of the item under test is unknown,
always set the LEAKAGE SENSITIVITY control (R77)
at the most sensitive setting. Rotate the control knob
counterclockwise toward the 0.3 mA position. This insures
the best test results and maximum protection for both the
operator and the item under test.

Low-Capacitance Items

The capacitance of most items is well below 1000 pF,
which implies a leakage current less than 0.3 mA when
tested at 1000 to 1200 volts. In such cases, the Tester can
be used with the LEAKAGE SENSITIVITY control
(R77) at the 0.3 mA position.

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Application Notes

Medium- to High-Capacitance Items

If an item has a capacitance greater than 1000 pF and its
capacitance-voltage point falls below the maximum output
line in Figure 3, it can be tested with the LEAKAGE
SENSITIVITY control (R77) at some intermediate
position between 0.3 mA and 12 mA.

Excessively High-Capacitance Items that Cannot be
Tested

If the capacitance of an item is so large that its
capacitance-voltage point falls beyond the maximum
output line in Figure 3, it is too large for this

Tester to

handle. This will be clear when attempting to test; since
even on a good appliance, a failure indication will be
signaled before the voltage reaches the desired value.

DC Testing

The maximum capacitance of an item that can be tested
with AC is approximately 10 nF; however, the capacitance
that can be tested with DC is virtually infinite. The upper
limit is unlikely to be encountered in practice.

The maximum output capability of the Tester in the DC
mode depends on the combination of the capacitance and
resistance of the item under test. When the capacitance

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and resistance of the item are known, Figure 4 can be used
to determine the approximate setting of the LEAKAGE
SENSITIVITY control (R77).

To use Figure 4, first draw a load line representing the
resistance of the item. As a guide, a load line representing a
resistance of 1 Megohm has been drawn. The ratio of the
desired test voltage to the voltage at the point where the
load line and the appropriate capacitance curve intersect
gives an approximate setting for the LEAKAGE
SENSITIVITY control (R77) in terms of the full travel of
the control knob.

If the desired test voltage falls to the right of the
capacitance curve, i.e., a ratio of greater than 1, the item
cannot be tested.

If the capacitance and resistance of the item under test are
unknown, the setting of the LEAKAGE SENSITIVITY
control (R77) can be determined by trial and error during
the testing of an identical known good item. Always set the
control to the most sensitive setting, as described above
for AC testing.

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Application Notes

Dielectric Withstand Testing of Low VAC
Appliances

Most 120 VAC tools and appliances are frequently tested
at 2 times working voltage +1000 volts (1240 V). Some
standards, however, call for other values of dielectric
withstand voltage. Such standards are issued by many
different authorities. The latest issue of the standard which
applies in each particular case should be consulted. A few
standard authorities are listed below in alphabetical order.

American National Standards Institute (ANSI)

rd

25 W. 43

St., 4th Floor

New York, NY 10036 USA

Canadian Standards Association (CSA)
178 Rexdale Boulevard
Rexdale, Ontario, Canada M9W1R3

International Electrotechnical Commission (IEC)
3 Rue de Varembe
CH-1221 Geneva, Switzerland 20
(Copies of IEC standards can be obtained from ANSI.)

Underwriters Laboratories, Inc. (UL)
333 Pfingsten Road
Northbrook, IL 60062 USA

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8.0

MAINTENANCE

Routine Maintenance

Certain routine maintenance procedures are necessary to
insure safe and correct operation of the Tester. These are
described below. Always make all of these inspections after
repairs to the Tester and at regularly scheduled intervals.
Make the inspections at least once a year, more often if the
set is in heavy use.

Mechanical Inspection (Exterior)

1. Case.

2. Clean the case, panel, test probe assembly and input

3. Panel

AVTM23-4J Rev 2 Dec 2010

Note that hinges and case lock function
properly. Check for cracks in the case or lid. Inspect
the condition of the handle.

power cord.

. Note that all knobs are secure on their shafts,
that all controls operate smoothly without binding and
all mounting screws are tight.

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4. Test Probe Assembly. Check for cracks in the

insulation. Note that the alligator clips and boots are
complete. Check and tighten screw connections at
clips.

5. Input Power Cord

Check cord plugs for cracked housings or broken pins.

6. Mechanically set the kilovoltmeter to zero.

7. Repair any defects found.

Mechanical Inspection (Interior)

The tester must be turned off and disconnected

F

1. To remove the panel assembly from the case:

from the power supply before it is removed
from its case.

a) Remove and set aside the four panel screws.

b) Carefully turn the case so that the panel assembly

faces down.

c) Slide the case up off the panel assembly.

. Check for cracks in the insulation.

WARNING

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Maintenance

WARNING
Hazardous voltages may be retained in the C-30
capacitor located on the AC/DC metering
circuits assembly board even after the tester

F

2. Clean any accumulated dust from the interior of the

3. Visually inspect all components and leads for defects.

4. Repair any defects found.

5. Remove the resistive load from capacitor C-30.

6. Reinstall the panel assembly in its case and replace the

has been turned off. Do not handle the tester
until this capacitor has been grounded with a
1K ohm resistor across the cap, and short­circuited for at least one minute.

d) Turn the panel assembly right side up and place

on a clean dry surface.

case and the panel assembly.

mounting screws.

Electrical Inspection

Perform the electrical inspection only after both
mechanical inspections have been completed. Before
performing this inspection, read the entire procedure given
below, as well as Sections 2, 5 and 6. Follow all safety
precautions.

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If the Tester does not function exactly as it should during
any of the following tests, refer to Section 9.0,
Troubleshooting Guide.

1. Setup

F

2. Dielectric Voltage-Withstand Circuit

When the TESTER GROUNDED lamp (DS5) is lit, the
dielectric withstand circuit can be checked. The following
user supplied items are required to conduct the tests:

a) With the power switch (CB1) off, connect the

input power cord (W2) to the Tester INPUT inlet
(P7); then plug the input power cord (W2) into a
grounded outlet.

b) Verify that the TESTER GROUNDED lamp

(DS5) is lit.

WARNING
If the tester grounded lamp (DS5) is not lit, do
not proceed further. Unplug the input power
cord (W2) and refer to Section 9.0,
Troubleshooting Guide.

a) 1.0 MΩ, 1/4 W resistor

b) 25 kΩ, 5 W resistor

c) stopwatch

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Maintenance

3. Zero Start (Reset) Test

a) Disconnect the high-voltage test probe assembly

(Wl) from the Tester.

b) Move the output receptacle slide to the far right to

cover the DC OUTPUT receptacle (J9). This
selects the AC output at J8.

c) Rotate the VOLTAGE CONTROL (T3) to the

first dot above the ZERO START (RESET)
position.

d) Press the HV OFF pushbutton. (S3).

e) Press the CONT pushbutton (S2). Observe the

following conditions:

- The HV ON lamp (DS3) should not

light. If not,

see Section 9.

- The kilovoltmeter (M1) should read zero.

f) Press the RESET pushbutton (S4).

g) Press the CONT pushbutton (S2). Observe the

following conditions:

- The HV ON lamp (DS3) should light.

- The kilovoltmeter (M1) should read a few
hundred volts.

h) Press the HV OFF pushbutton (S3). The HV ON

lamp (DS3) should go out.

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i) Rotate the VOLTAGE CONTROL (T3)

counterclockwise to the ZERO START (RESET)
position.

j) Press the CONT pushbutton (S2). Observe the

following conditions:

- The HV ON lamp (DS3) should light. If not, see
Section 9.

- The kilovoltmeter (M1) should read zero.

k) Press the HV OFF pushbutton (S3). The HV ON

lamp (DS3) should go out.

4. Leakage Sensitivity Test

a) Set the power switch (CB1) to the OFF position.

b) Connect the high-voltage test probe assembly

(W1) to the AC OUTPUT receptacle (J8).

c) Connect the 1.0 MΩ resistor (user supplied)

between the leads of the high-voltage test probe
assembly (W1)

d) Insulate the resistor/test probe assembly for at

least 4000 volts; locate the assembly to prevent
accidental contact with persons.

e) Set the LEAKAGE SENSITIVITY control (R77)

to 0.3 mA.

f) Rotate the VOLTAGE CONTROL (T3) to the

ZERO START (RESET) position.

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Maintenance

g) Set the power switch (CBl) to the ON position.

The switch should light.

WARNING

Do not touch or permit anyone else to touch the

F

resistor/test probe assembly.

h) Press the CONT pushbutton (S2). The HV ON

lamp (DS3) should light.

i) Slowly rotate the VOLTAGE CONTROL (T3)

clockwise while observing the kilovoltmeter (M1)
indication. When the kilovoltmeter (M1) shows
between 100 and 400 volts, the FAILURE lamp
(DS2) should light and the audible alarm should
sound.

j) Rotate the VOLTAGE CONTROL (T3) to the

ZERO START (RESET) position.

k) Repeat steps 1 through 10, using the 25 kΩ

resistor (user supplied) instead of the 1.0 MG
resistor and with the LEAKAGE SENSITIVITY
control (R77) set at 12 mA instead of 0.3 mA.

l) Repeat steps ‘a’ through ‘k’ with the high-voltage

test probe assembly (W1) connected to the DC
OUTPUT receptacle (J9).

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 Breakdown Sensitivity Test

m) Set the power switch (CB1) to the OFF position.

Disconnect the 25 kΩ resistor (user supplied).

1. Connect the high-voltage test probe assembly

(W1) to the AC OUTPUT receptacle (J8).

2. Place the black and red alligator clip leads of the

high-voltage test probe assembly (W1)
approximately 1/16 inch apart. They must not
touch each other.

3. Insulate the test probes for at least 4000 volts and

locate the test probe alligator clips to prevent
accidental contact with persons.

4. Rotate the VOLTAGE CONTROL (T3) to the

ZERO START (RESET) position.

5. Set the power switch (CB1) to the ON position.

The switch should light.

F

6. Press the CONT pushbutton (S2). The HV ON

lamp (DS3) should light.

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WARNING
Do not touch or permit anyone else to touch the
high-voltage test probe alligator clips.

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Maintenance

7. Slowly rotate the VOLTAGE CONTROL (T3)

clockwise while observing the kilovoltmeter (M1)
indication. When there is an arc between the high­voltage test probe assembly (W1) alligator clips,
the FAILURE lamp (DS2) should light and the
audible alarm should sound.

8. Rotate the VOLTAGE CONTROL (T3) to the

ZERO START (RESET) position.

9. Set the power switch (CB1) to the OFF position.

NOTE: If no arc occurs between the test probe

alligator clips, check that they are spaced
approximately 1/16 inch apart and repeat
the test.

10. Connect the high-voltage test probe assembly

(W1) to the DC OUTPUT receptacle (J9) and
repeat steps 2 through 9.

 One-Second Test

1. Rotate the VOLTAGE CONTROL (T3) to the

ZERO START (RESET) position.

2. Disconnect the high-voltage test probe assembly

(W1) from the Tester.

3. Set the power switch (CB1) to the ON position.

The switch should light.

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If the dielectric withstand circuit functions properly and all
other circuit tests have been completed successfully, the
electrical inspection of the Tester may be considered
complete.

If the dielectric withstand circuit does not function
properly, refer to Section 9.0, Troubleshooting Guide.

4. Press the ONE SEC pushbutton (S1). The HV

ON lamp (DS3) should light and stay on for 1 to

1.3 seconds. Time the high-voltage-on period with
a stopwatch.

5. Set the power switch (CB1) to the OFF position.

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Calibration

F

The following items are required for the calibration
procedure:

 Insulated screwdriver.

 For the AC mode of the Tester, a standard AC

voltmeter with a range of 4000 volts rms and overall
accuracy of 0.5% or better.

 For the DC mode of the Tester, a standard DC

voltmeter with a range of 5000 volts DC and overall
accuracy of 0.5% or better.

Setup

Maintenance

WARNING
Because of the dangerous voltages developed
during operation of the Tester, the following
calibration should be carried out only by
qualified personnel.

1. Remove the panel assembly from the Tester case.

Refer to step l of the Mechanical Inspection (Interior)
procedure for details on removal of the panel
assembly.

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The interior of the tester develops dangerous
voltages while in operation. These voltages
may be retained even after the unit has been

F

2. Set up the Tester according to the setup procedure

Calibration Procedure

1. With the power switch (CB1) off, connect the high-

2. Insulate the standard voltmeter and all leads from

turned off. Therefore, be sure not to make
contact with any of the unit’s high-voltage
components while performing the calibration.

given for conducting an electrical inspection of the
unit.

voltage test probe assembly (W1) to the AC OUTPUT
receptacle (J8) and connect the standard AC voltmeter
between the alligator clips of the high- voltage test
probe assembly (W1).

ground and from each other for at least 4000 volts;
locate the standard voltmeter to prevent accidental
contact with persons.

WARNING

3. Rotate the VOLTAGE CONTROL (T3) to the

ZERO START (RESET) position.

4. Set the LEAKAGE SENSITIVITY control (R77) to

0.3 mA.

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Maintenance

5. Set the power switch (CB1) to the ON position. The

switch should light.

WARNING
While the tester is energized, do not touch or

F

6. Press the CONT pushbutton (S2). The HV ON lamp

7. Slowly rotate the VOLTAGE CONTROL (T3)

If there is a discrepancy, use the insulated screwdriver to
rotate the AC CAL pot (R91) until the standard voltmeter
and the Tester kilovoltmeter (Ml) show the same voltage.

permit anyone else to touch any exposed parts.

(DS3) should light.

clockwise while observing the standard voltmeter. Set
the voltage to 3 kV. The Tester kilovoltmeter (M1)
should also read 3 kV ±2% of full scale.

NOTE

8. Check several other voltages and be sure that all are

AVTM23-4J Rev 2 Dec 2010

: The calibration pots are located on the

within tolerance.

AC/DC metering circuits assembly board
(A3).

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9. After the kilovoltmeter (M1) is calibrated and checked,

10. Repeat steps 1 through 9 with the high-voltage test

11. Unplug the input power cord (W2), reinstall the panel

rotate the VOLTAGE CONTROL (T3) to the ZERO
START (RESET) position, press the HV OFF
pushbutton (S3) and set the power switch (CB1) to the
OFF position.

probe assembly (W1) connected to the DC OUTPUT
receptacle (J9) and the standard DC voltmeter (user
supplied) connected between the alligator clips of the
high- voltage test probe assembly (W1). Set the voltage
to 4 kV and use the DC CAL pot (R97) to correct for
any discrepancy between the standard DC voltmeter
and the Tester kilovoltmeter (M1).

assembly into its case and replace the mounting
screws.

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9.0

TROUBLESHOOTING GUIDE

Repairs

Megger Instruments maintains a complete instrument
repair service. Should this instrument ever require repair,
we recommend that it be returned to the factory for repair
by our instrument specialists. When instruments are
returned for repair, either in or out of warranty, they
should be shipped Prepaid and Insured, and marked for
the attention of the Repair Service Manager.

Before troubleshooting is attempted, the Tester should be
completely checked for proper operation as described in
Section 8.0, Maintenance.

NOTE

Figure 5 shows some of the internal components of the
Tester and gives their schematic reference numbers.
Section 10.0, Replaceable Parts List, identifies all

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: The Tester develops dangerous interior

voltages and employs printed circuit card
construction, therefore, repairs must be made
only by qualified persons.

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components used in the Tester and gives the Megger Part
Numbers. For safety, it is recommended that only Megger
replacement parts be used when making repairs to the
Tester.

Refer to the AC/DC High Pot Tester schematic in Section

10.0, Replaceable Parts List, in this manual for any
required circuit details.

Contact the factory if major problems are encountered
while troubleshooting or making repairs or if assistance is
required.

After repairs have been made, always perform a complete
inspection of the Tester, as detailed in Section 8.0,
Maintenance.

The brief troubleshooting guide that follows identifies
some of the problems that may interfere with the proper
operation of the Tester.

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Troubleshooting Guide

Figure 5 Internal View of Tester

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PROBLEM PROBABLE CAUSE

TESTER GROUNDED lamp
(DS5) not lit.

TESTER GROUNDED

 No voltage at service

outlet for the Tester

 Ground wire open or

ground contact of service
outlet not grounded

 “Hot” and “neutral” wires

on service outlet inter­changed (l20V operation)

 Defective input power

cord (W2)

 Defective opto-isolator

(U4)

 Defective TESTER

GROUNDED lamp (DS5)

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Troubleshooting Guide

DIELECTRIC WITHSTAND

PROBLEM PROBABLE CAUSE

HV ON lamp (DS3) lit.
Kilovoltmeter (M1) reads zero
when VOLTAGE CONTROL
(T3) is rotated toward MAX
position.

No output voltage.

Failure indications may occur

HV ON lamp (DS3) lit.
Kilovoltmeter (M1) reads zero
when VOLTAGE CONTROL
(T3) is rotated toward MAX
position.

Output voltage present.

One-second or continuous
test not functioning.

HV ON lamp (DS3) not lit.
Kilovoltmeter (M1) reads zero
when VOLTAGE CONTROL
(T3) is rotated toward MAX
position.

No output voltage. TESTER
GROUNDED lamp (DS5) lit
(IC U1, U4 operating).

Pressing HV OFF pushbutton
(DS3) does not turn off high

 High-voltage circuits

internally shorted or open

 Defective kilovoltmeter

(M1)

 Defective meter selector

microswitches (S7, S8)

 Defective diodes (CR40,

CR41)

 Defective pushbutton (S1

for one-second test, S2
for continuous)

 Defective relay (K1)

 Defective IC (U2, U3)

 Defective transistor (Q3,

Q4, Q5)

 Defective pushbutton

(S3)

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PROBLEM PROBABLE CAUSE

voltage.  Defective IC (U2, U3)

FAILURE lamp (DS2) and
audible alarm (LS1) do not
operate when failure occurs.
High voltage does not switch
off or power switch (CB1) trips
when failure occurs

FAILURE lamp (DS2) and
audible alarm (LS1) do not
operate when failure occurs.
High voltage switches off
when failure occurs

Returning VOLTAGE
CONTROL (T3) to ZERO
START (RESET) position or
pressing RESET pushbutton

(S4) does not turn off failure

signals

DIELECTRIC WITHSTAND

 Defective transistor (Q3,

Q4, Q5)

 Defective LEAKAGE

SENSITIVITY control
(R77).

 Defective IC (U1 U2, U3).

 Defective surge protector

(CR4, CR5).

 Defective IC (U1, U3).

 Defective transistor (Q1,

Q2)

 Defective opto-isolator

(U5)

 Defective IC (U1, U2, U3)

 Defective RESET

pushbutton (S4)

 Defective ZERO START

(RESET) contact

 Defective transistor (Q2)

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10.0

REPLACEABLE PARTS LIST

Schematic
Symbol

C1,C11*,C20* Capacitor, .22 μF, 50V 17127-13

C2* Capacitor, 1000 μF, 25V 23908-1

C3* Capacitor, .01 μF, 1000V 9865-25

C4* Capacitor, 47 μF, 20V 17132-3

C5*,C13*,C14* Capacitor, .47 μ , 100V 19836-8

C6* - C8*,C17* Capacitor, 1000 pF, 100V 17127-1

C9* Capacitor, 470 pF, 1000V 7950-24

C10* Capacitor, .047 μF, 100V 17127-2

C12* Capacitor, .01 μF, 100V 17127-9

C15* Capacitor, .01 μF, 630V 19836-10

C16* Capacitor, .001 μF, 1000V 7950-12

C19*, C23* Capacitor, .1 μF. 50V 17127-7

C18*,C21*,C22* Capacitor, 4700 pF, 100V 17127-4

C30*** Capacitor, .25 μF, 6000V 25731-1

CB1 Circuit Breaker,2-

Description Part No.

23964

Pole,250V,1A

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Schematic
Symbol

CR1*,CR3* Bridge Rectifier, VM18 22921

CR2*,CR6*­CR27*, CR35**,
CR4O***,
CR41***

CR42***, Diode, H463-5 19173

CR4*,CR5* Transzorb, 1.5 KE20CA 17040-5

DS1 Neon Part of CB1 —

DS2** FAILURE LED (Yellow) 17142-1

DS3** HV ON LED (Red) 17142

DS5 TESTER GROUNDED

E1*,E13*** Male Quick-Disconnect Tab 17029-1

E5,E6 Insulated Standoff 23063

E9*,E10*,E11* 2-Pin Male Strip 22931-2

F1* Subminiature Fuse, 1/16A 25421-1

J8,J9 High-voltage Receptacle 23978-2

K1* Relay Coil 12 VDC,

LS1* Alarm, AT-03 25198

M1 Kilovoltmeter (5 kV Full Scale) 19937-9

Description Part No.

Diode, lN4l48 11637-40

4499-8

Neon (White)250V, 1/3W

25114

Contact 250 VAC, 3A

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Replaceable Parts List

Schematic
Symbol

P7 Recessed Power Inlet, 250V,

Q1*-Q5* Transistor, 2N3904 11638-62

R26*,R33*,
R37*,R42*,R48*,
R66*

R1* Resistor, 24.3 KΩ, 1/4W, ±1% 12398-144

R2* Resistor, 169 KΩ, 1/4W, ±1% 12398-92

R3* Resistor, 33 kΩ, 1/2W, ±5%

R4* Resistor, 220Ω, 2W, ±5%

R5*,R54* Resistor, 47 kΩ, 1/4W, ±5%

R6* Resistor, 15 kΩ, 1/4W, ±5%

R7*,R68*,R76** Resistor, 820Ω, 1/4W ±5%

R8* Resistor, 470Ω, 1/4W, ±5%

R9* Resistor, 430Ω, 1/4W, ±5%

R10* Resistor, 10 kΩ 1/4W, ±5% 4501-506

Description Part No.

18305

6A

Resistor, 1 MΩ, 1/4w, ±5%
Carbon Composition

Carbon Composition

Carbon Composition

Carbon Composition

Carbon Composition

Carbon Composition

Carbon Composition

Carbon Composition

4501-508

4501-186

4501-407

4501-514

4501-71

4501-69

4501-575

4501-576

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Schematic
Symbol

R11*,R23* Resistor, 681Ω, ±1%, RN55D 12398-71

R12*,R13*,R19*,
R30*,R31*,R38*,
R39*,R45*,R46*,
R50*,R60*,R65*

R14* Resistor, 10 MΩ, 3W, ±1%, 6

R15*,R90*** Resistor, 37.4 kΩ, ±1%,

R16* Resistor, 20 kΩ, ±1%, RN55D 12398-1

R17* Resistor, 11 kΩ, ±1%, RN55D 12398-176

R18* Potentiometer, 10 kΩ

R20* Resistor, 1 kΩ, ±1%, RN55D 12398-16

R21* Resistor, 19.6Ω, ±1%, RN55D 12398-191

R22* Resistor, 200Ω ±1%, RN55D 12398-4

R24* Resistor, 56 kΩ, 1/4W, ±5%

R25* Resistor, 680Ω, 1/4W, ±5%

R27*,R36* Resistor, 5.1 MΩ, 1/4W,±5%

Description Part No.

Carbon Composition

Resistor, 100 kΩ, 1/4W, ±5% 4501-91

10646-17

kV

12398-19

RN55D

Carbon Composition

Carbon Composition

Carbon Composition

12340-10

4501-90

4501-66

4501-540

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Replaceable Parts List

Schematic
Symbol

R29*,R49* Resistor, 470 kΩ, 1/4W, ±5%

R32* Resistor, 360 kΩ, 1/2W, ±5%

R34*,R35*,R40*,
R41*,R43*,R67*

R28*,R44*,R47* Resistor, 200 kΩ, 1/4W, ±5%

R51* Resistor, 392 kΩ, ±1%,

R52* Resistor, 2 MΩ, ±1%, RN55D 12398-193

R53* Resistor, 330 kΩ, 1/4W, ±5%

R55* Resistor, 150Ω, 1/4W, ±5%

R56*,R57* Resistor, 1 kΩ, 1/4W, ±5%

R58* Resistor 1 MΩ, ±1%, RN55D 12398-81

R59*,R61* Resistor, 100 kΩ, ±1%,

R62* Resistor, 5.62 kΩ, ±1%,

Description Part No.

4501-513

Carbon Composition

4501-536

Carbon Composition

Resistor, 510kΩ, 1/4W, ±5%
Carbon Composition

Carbon Composition

RN55D

Carbon Composition

Carbon Composition

Carbon Composition

RN55D

RN55D

4501-509

4501-525

12398-192

4501-510

4501-545

4501-51

12398-27

12398-7

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Schematic
Symbol

R63* Resistor, 4.02 kΩ, ±1%,

R64* Resistor, 100 kΩ, 1W, ±5%

R67* Resistor, 4.7 kΩ, 1/4W, ±5%

R69* Resistor, 2 MΩ, 1/4W, ±5%

R70*,R71*,R72* Resistor, 22 kΩ, 1/4W, ±5%

R75** Resistor, 10 kΩ, 2W, ±5%

R77** Potentiometer, 50 kΩ 17135-7

R91*** Potentiometer, 20 kΩ 23986-5

R92*** Resistor, 15 kΩ, ±1%, RN55D 12398-15

R93***,R94*** Resistor, 8 MΩ 5W, ±1%, 10

R96*** Resistor, 5.36 kΩ, ±1%,

R97*** Potentiometer, 5 kΩ 23986-4

S1**-S4** Pushbutton Switch 17137

S6* Line Selector Switch 18620

Description Part No.

12398-131

RN55D

4501-371

Carbon Composition

4501-53

Carbon Composition

4501-511

Carbon Composition

4501-554

Carbon Composition

4501-423

Carbon Composition

10646-45

kV

12398-52

RN55D

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Replaceable Parts List

Schematic
Symbol

S7***, S8 **** Microswitch 25727

T1 Transformer, Primary

T2 High-Voltage Transformer 25140

T3 Autotransformer (120V Tester) 6408-2

T3 Autotransformer (240V Tester) 17787

U1* Integrated Circuit, Schmidt

U2*,U3* Integrated Circuit, Quad Op

U4*,U5* Integrated Circuit, Opto-

VR1* Voltage Regulator, LM340AT 23691-5

W1 High- Voltage Test Probe

W2 Input Power Cord (120V

W2 Input Power Cord (240V

- Zero Start Contact Mounted on

- Output Receptacle Slide 25722

AVTM23-4J Rev 2 Dec 2010

Description Part No.

25141
115/230V, Secondary 16V
C.T. @0.4A

25045-8
Trigger Quad Nand Gate, 4093

25045-27
Amp, LM324

25257
Isolator, IL-250

25149
Assembly

17032
Tester)

17032-2
Tester)

23202
T3

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Schematic
Symbol

- Knob (for T3) 4690-25

- Knob (for R77) 25146

- Case Assembly 10998

- Lid Assembly 22389-4

- Instruction Card 26112

NOTE: The following components on PC Board Assembly (A1),
P/N 23138, are not used:

CR3, E9, E10, R14, R15, R16, R17, R18, R19

*Part of PC Board Assembly (Al), P/N 25138
**Part of PC Board Assembly (A2), P/N 25134
***Part of PC Board Assembly (A3), P/N 25729

Description Part No.

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11.0

WARRANTY & REPAIR

Warranty

All products supplied by Megger are warranted against all
defects in material and workmanship for a period of one
year following shipment. Our liability is specifically limited
to replacing or repairing, at our option, defective
equipment. Equipment returned to the factory for repair
will be shipped Prepaid and Insured. The warranty does
not include batteries, lamps or tubes, where the original
manufacturer’s warranty shall apply. WE MAKE NO
OTHER WARRANTY.

The warranty is void in the event of abuse or failure by the
customer to perform specified maintenance as indicated in
this manual, or if the instrument is connected to external
power sources other than those specified in this manual.

Repairs

Megger maintains a complete instrument repair service.
Should this instrument ever require repairs, we
recommend it be returned to the factory for repair by our
instrument specialists. When returning instruments for

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repairs, either in or out of warranty, they should be
shipped Prepaid and Insured and marked for the attention.
of the Instrument Service manager.

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AVTM23-4J Rev 2 Dec 2010

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Figure 6
Schematic Diagram of
Megger ACV/DC High Pot Testers
230425 & 230425-1